Spark-plug tester



W. S WOLFF.

SPARK PLUG TESTER.

APPLICATION FILED mmze. 1919.

1,332,017. Patented Feb. 24,1920.

zwvwvron:

BYAL'S .AT RJVEY:

To all whom it may concern.

WILLIAM S AMUEL WOLFE, OF ST. PAUL, MINNESOTA.

SPARK-PLUG TESTER.

Be it known that I, VILLIAM S. lVoLFF a citizen of the United States, residing at gt. Paul, in the county of Ramsey and State of Minnesota, have invented a new and useful Spark-Plug Tester, of which the following is a specification.

My invention relates to improvements in testers for the spark plugs of internal combustion engines.

It has been determined by demonstration that spark plugs which will spark properly between electrodes in the open air or under atmospheric pressure only, will not properly perform their function when in use, owing to the fact that the pressure within the engine cylinders or explosion chambers in which they are employed, retard sparking; means have therefore been invented for testing spark plugs under air pressure much higher than the atmospheric pressure; but the only device I know of as designed for that purpose is so imperfect as to be practically useless, because it tests the spark plug im a very small space filled with static air under pressure, and it has been demonstrated by actual experiments that in statlc compressed air, especially in a small space, when an electric current is passed through it, a coating of nitrous oxid is formed on the spark plug and the electric current short circuits'out of the space along said coating instead of jumping through the space and causing a spark. The main object of my invention is to overcome the last mentioned ,difliculty, and to that end I provide in my device means for maintaining constant circulation of fresh air to the spark plug while it is being tested.

In the accompanying drawing Figure 1 is a top or plan view of my improved spark plug tester. Fig. 2 is a partly sectional side elevation of Fig. 1 with the airsupply tank omitted.

Referring to the drawing by reference numerals, 3 designates a wooden base upon which is secured by screws 4. a cylinder 5, having a solid bottom'6, and its top closed by a glass lens 7 which is held in place by a soft packing ring 8 anda threaded collar 9.

- The cylinder or chamber 5 is connected to a compressed air reservoir 10 by a pipe 11 having a. valve 12; it is further provided with an air outletpipe 13 having a valve 14. The, chamber is further provided with an Specification of Letters Patent.

Patented Feb. 24, 1920.

Application filed March 28, 1919. Serial No. 285,892.

air pressure gage 15, and several plugs like 16', 17, 18, each of which is threaded into the chamber with such difi'e'rent number of threads to the inch as is customary on the different spark plugs found in the market. In either of the holes for said plugs the spark plug to be tested is inserted like the plug 19 in the drawing. The chamber is also provided with a contact post 20.

Mounted upon the base is a suitable number of battery cells 21, and an induction coil or transformer 22, which are connected together and to the post 20 and to the post 20 of the spark plug by circuit wires 24, 25, 26, 27, 28, 29, 30, 31, 32, which in Fig. 1 is shown partly in dotted lines as concealed in the base 3. In said circuit is inserted a switch 33. The binding posts 34, 35, and the secondary circuit wire 29 are so readily understood by electricians that no further description is here considered necessary.

In operation of the device the spark plug to be tested is screwed into such hole in the air chamber 5 as has got screw threads to fit those on the plug. The wire 31 is then connected to the plug and the large valve 12 and the small valve 1% opened and so regulated that the compressed air will move through the chamber under such pressure as it may be desired to test the plug; the switch 33 is then closed and the sparking process watched through the lens 7. If the plug sparks properly under a pressure higher than that resulting from the compression of the gas in the explosion chamber of the engine in which the plug is to be used, then the plug is all right, and if it does not stand such test, it needs repair or else replacing by a good plug.

By the use of-a properly tested spark plug and properly strong battery cells in this kind of device, it is evident that if the plug will not spark properly there' must be some I pressure high enough to stand some reduction by the partial escape of air at the valve 14:.

What Iclaim is:

1. A spark plug tester comprising an air chamber with a sight glass through which to look into it, means for holding spark plugs inserted in the chamber, an electric circuit in which the spark plug is located, and means for passing a constant current of compressed air through the air chamber,

2. The structure specified in claim 1, said means for holding the plugs consisting of screw-threaded holes in the sides of the chamber, said holes adapted to fit the various sizes and threads of spark plugs.

3. The structure specified in claim 1, and means for regulating the air pressure in the chamber, and a pressure gage indicating the pressure in the chamber.

4. The method of testing spark plugs, which consists in passing an electric current through the plug and at the same time passing a current of compressed air along in pressing contact with the sparking end of 25 the plug.

In testimony whereof I affix my signature.

\VILLIAM SAMUEL VVOLFF. 

